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-   -   Rotor Blade cross section (https://www.pprune.org/rotorheads/87573-rotor-blade-cross-section.html)

John Bicker 23rd Apr 2003 23:53

GR
 
Don't get ya tits in a tangle. This is an internet forum isn't it? Read the bottom of the page!

Yes I am a maintainer myself of 20 odd years. The point that was brought up was "is this really a question that could be answered?"


Are the airfoils used for modern helicopter rotor blades symmetrical or un-symmetrical.
It would appear to be a question that is asked by the CAA. Just what is the point?

Does it refer to the fleet in general or those in current production?

How long is a piece of string? Seems to be Belgrano-speak.

Lu Zuckerman 24th Apr 2003 03:32

The troll speaks.
 
To: Golden Rivet


Are the airfoils used for modern helicopter rotor blades symmetrical or un-symmetrical.
The simplest answer to your question is "Yes". "Yes" and "No".
The "No" reflects Nick Lappos' response about asymmetrical rotor blades.

;)

CAC Runaway 26th Apr 2003 20:19

More and more helicopters are going the way of asymmetric aerofoil sections for a number of reasons. I fly the Westlands Lynx amongst others, for example, which has the BERP blade (as does the EH/US101) and has a paddle tip and an asymmetric section along its length. You do have the problem of movement of centre of pressure but it is removed by the use of hydraulics (it is not flyable without hydraulic assistance). Most large modern aircraft are unflyable without hydraulics. The asymmetric aerofoil give a much better figure of merit than a symmetriacl one. The BERP tip is designed to reduce retreating blade stall (the notch re-energises the flow over the tip), improve compressibility problems on the advancing side at high speed (using a thin aerofoil). The area of the tip is spread equally for and aft off the main blade to reduce CofP movement problems.


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